Recently, NAS (network attached storages) have received attention as one type of storage systems that are installed in data centers or the like. A NAS is configured using an application server, which is provided on the same LAN (local area network) as a host computer, and a storage system that is connected subordinately to the application server. The application server accepts file access requests by file designations received from the host computer via the LAN, and sends disk access requests to a subordinate storage system. The storage system carries out the reading or writing of data in response to the disk access requests from the application server. It is noted that a “file access request” means a read request, a write request, or any other request of this kind that is carried out through a file system.
For the backup of data with a NAS, a backup server different from the application server is provided on the LAN. The backup server reads out backup data via the LAN from the storage system subordinate to the application server, and backs up the data in a backup device, such as a tape library. Furthermore, by providing the storage system with a function for writing to the backup device, a method for backing up data from the storage system without using a backup server has also been contrived.
However, in backup methods in which a backup server is not utilized, the application server is no longer able to obtain device control information from the backup server. It should be noted that what is here referred to as device control information may be characteristic information about the backup device or information about storage capacity, for example.
Furthermore, if the storage system is provided with a function for writing to the backup device, then this may influence the routine processing of the storage system. This influence on the routine processing becomes larger as the amount of the data that is backed up onto the backup device becomes larger or as the number of backup devices to back up on becomes larger and then the speed of the routine processing may become sluggish. It should be noted that what is referred to as routine processing here may be, for example, writing or reading data that are processed in response to a disk access request from the application server. It is also noted that a “disk access request” means a read request, a write request, or any other request of this kind that is carried out without utilizing a file system.